1. Field of the Invention
The present invention relates to a microphone unit mounting structure, for example, for a portable telephone set wherein a microphone of a small size is formed as a unit together with a holder therefor and mounted in the inside of a body of the portable telephone set.
2. Description of the Related Art
Conventionally, in order to mount a microphone for a portable telephone set or the like, various mounting methods such as a method wherein a microphone itself is soldered to a printed circuit board or another method wherein a microphone is secured to a front case of a body of the portable telephone set or the like and leads from the microphone are soldered to a printed circuit board are used to electrically connect the microphone and the printed circuit board to each other.
However, in recent years, as a portable telephone set exhibits remarkable popularization, also the number of manufactured units exhibits a remarkable increase. Therefore, various mounting structures and connection methods for a microphone which achieve augmentation of the production efficiency have been proposed. Typical mounting structures and connection methods are described below.
FIGS. 10 and 11 show one of such conventional mounting structures for a microphone as described above. Referring to FIGS. 10 and 11, a disk-shaped microphone 101 is fitted in a microphone holder 102 made of rubber and having a ring shape with a flange, and a microphone connector 103 of conductive rubber is placed on one face of the microphone 101 to form a microphone unit 104. The microphone holder 102 is force fitted in a microphone unit force fit rib 106 provided on an inner face of a front case 105 of a body typically of a portable telephone set to secure the microphone unit 104 to the front case 105. The microphone connector 103 contacts under pressure with a printed circuit board 107 (to make the microphone connector 103 of conductive rubber collapse) to electrically connect the microphone 101 and the printed circuit board 107 to each other. A sound passing hole 108 is formed in the front case 105.
FIGS. 12 and 13 show another mounting structure for a microphone. Referring to FIGS. 12 and 13, a disk-shaped microphone 201 is placed on a microphone connector 202 with spring terminals and fitted in a microphone holder 203 made of rubber to form a microphone unit 204. The microphone holder 203 is force fitted in a microphone unit force fit rib 206 provided on an inner face of a front case 205 of a body typically of a portable telephone set to secure the microphone unit 204 to the front case 205. Spring terminals 202a of the connector 202 contact under pressure with a printed circuit board 207 (to deform the spring terminals 202a) to electrically connect the microphone 201 and the printed circuit board 207 to each other. A sound passing hole 208 is formed in the front case 205.
However, since reduction in size and weight has proceeded with portable telephone sets in recent years, and also from a reason that, particularly with portable telephone sets of the foldable type, it has become a requirement that a display section has an increasingly large screen, there is a tendency that the thickness of the portable telephone set when it is folded around a hinge member such that upper and lower portions of the body are overlapped with each other is reduced because there is a limitation to reduction of the width and the length of the body.
However, in the conventional microphone unit mounting structures described above, a microphone connector is placed on one face of a microphone and is held between the microphone and a printed circuit board to establish electric connection between the microphone and the printed circuit board. Therefore, a space in which the microphone connector is to be accommodated is required in addition to the thickness of the microphone between the front case and the printed circuit board. Further, as the thickness of the body, the sum of the thickness of the microphone, the thickness of the connector and the thickness of the printed circuit are required with certainty.
Accordingly, in order to reduce the thickness of the body of the portable telephone set, it is necessary to reduce the thickness of each of the parts such as the microphone and the microphone connector. In other words, the conventional microphone unit mounting structures described above has a problem in that, from a restriction to the dimension of the sum of the thickness of the microphone and the thickness of the microphone connector and the printed circuit board, the thickness of the body cannot be reduced.
It is an object of the present invention to provide a microphone unit mounting structure wherein the thickness of a body of a portable telephone set or the like can be reduced without being restricted by the dimension of the sum of the height of a microphone and the thickness of a microphone connector and a printed circuit board.
In order to attain the object described above, according to the present invention, there is provided a microphone unit mounting structure for mounting a microphone on a body member having a front case, comprising a microphone connector electrically connected to the microphone, a microphone holder for holding the microphone together with the microphone connector thereon to form a microphone unit, and a printed circuit board, the microphone connector having a projecting portion projecting outwardly therefrom farther than an outer peripheral edge of the microphone and electrically connected to the printed circuit board, the printed circuit board having a microphone unit relief hole formed therein, the microphone unit being held on the front case of the body member in such a state that part of the microphone unit is received in the microphone unit relief hole.
With the microphone unit mounting structure, the microphone connector and the printed circuit board are connected to each other at a location spaced away from the microphone and the thickness of part of the microphone unit can be relieved by the microphone unit relief hole of the printed circuit board. Therefore, the distance between the printed circuit board and the inner face of the front case can be confined within the range of the thickness of the microphone. Further, the installation thickness of the printed circuit board remains within the range of the thickness of the microphone unit, and also the installation thickness of the electric connection portion between the microphone connector and the printed circuit board remains within the range of the thickness of the microphone unit. Therefore, the body member can be formed with a small thickness.
Preferably, the projecting portion of the microphone connector includes a spring terminal. With the microphone unit mounting structure, the electric connection can be established through the spring without using solder. In this instance, preferably the microphone holder has a terminal stopper projecting outwardly therefrom such that deformation of the spring terminal of the microphone connector by more than a predetermined amount can be restricted by the terminal stopper. With the microphone unit mounting structure, an inclination of the spring terminal which occurs with respect to the printed circuit board can be suppressed, and consequently, a stabilized electric connection state can be maintained. Further, the spring terminal can be protected to prevent deformation of or damage to the spring terminal upon assembly.
Alternatively, the projecting portion of the microphone connector may be electrically connected to the printed circuit board through a conductive rubber connector. Also with the microphone unit mounting structure, the electric connection can be established through the spring without using solder.
Preferably, the front case has a microphone unit force fitting rib formed on an inner face thereof, and the microphone unit is force fitted in the microphone unit force fitting rib to hold the microphone unit on the front case. With the microphone unit mounting structure, the microphone unit can be mounted simply.
Preferably, the microphone unit is held down by a holding down plate from the opposite side of the front case together with the printed circuit board to secure the microphone unit to the front case together with the printed circuit board. With the microphone unit mounting structure, the mounting structure is tough against an impact.
The above and other objects, features and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings in which like parts or elements are denoted by like reference symbols.